In known cases of this type, action on the thumb piece permits unlocking the catch means but the cover remains practically closed on the base, so that the user must open it, for example by inserting a fingernail in the free space between the base and the cover. Moreover, the cover tends to return to closed position by gravity, which militates against a reasonable use of the case.
To overcome this drawback, it is known to provide a return spring, for example a helicoidal spring wound about the articulation axle and whose ends bear respectively on the base and the cover. The mounting of such a spring is complicated and difficult for cases of small dimensions such as compacts. Moreover, the return force is difficult to calibrate so as not to trigger a too abrupt and/or too complete opening. Moreover, such a system is difficultly adaptable to cases comprising an internal platform which must also be articulated on the base and open to give access to a product to be used such as a cake of face powder.